1. Field of the Invention
The present invention relates to a bushing, and more particularly to a simply-structured bushing free from too large play between facing sliding surfaces thereof.
2. Description of the Prior Art
Cylindrical bushings have been used in coupling portions of a suspension of a vehicle. Recently, in order to realize an improved ride of the vehicle as well as the stability and controllability thereof, various types of bushings which have large rigidities in directions perpendicular to the axial direction thereof, and enable free rotation and twistable rocking of suspension arms, have been proposed. One of the above-described bushings is disclosed in Japanese examined Utility Model publication (Jikko) No. Sho 63-44572, and hereinafter will be briefly explained with reference to FIG. 24.
In the drawing, an outer cylinder 1 is press-fitted into a cylindrical retaining member 5 for a suspension arm. An inner cylinder 2 is coaxially disposed within the outer cylinder 1. The axially central portion of the inner cylinder 2 is radially expanded to form a spherical expanded portion 21. Inserts 3' made of resin are slidably in contact with the outer surface of the spherical expanded portion 21. The inserts 3' are inserted from both open ends of the outer cylinder 1. Seal rings 6, each having a lip portion 61, are disposed outside the inserts 3', and backup rings 7 are disposed outside the seal rings 6. These members are fixed in position by caulking the both open ends of the outer cylinder 1.
The conventional bushing having the above-described structure prevents the suspension arm from moving in directions perpendicular to the axial direction thereof, and enables it to rotate about the inner cylinder 2, and twistingly rock along the expanded portion 21 in the directions shown by the arrows in FIG. 24.
However, the above-described conventional bushing has a problem that when an external force is applied to the inserts 3' outwardly with respect to the axial direction thereof, the inserts 3' move outwardly and deform the seal rings 6, thereby decreasing the sealing property of the seal rings 6 and generating too large play between the inserts 3' and the expanded portion 21. Accordingly the stability and controllability of the vehicle are decreased.
The above-described conventional bushing has other problems of requiring troublesome works for preparing and assembling parts such as seal rings 6 and backup rings 7, and also requiring the caulking work of the outer cylinder 1, thereby increasing the production costs.
The problem that the number of parts is large is also encountered with other conventional bushings disclosed in Japanese unexamined Utility Model publications (Jikkai) Nos. Sho 61-49143 and Sho 62-110619.